I've been keeping track of my hobby spending for a couple of years, after deciding that I needed to get it in control. Last year, I spent about £500, though my net spend (i.e. deducting hobby stuff sold) was actually negative, which was a first. This year, I've spent about £100, so need to rein it in a bit. It's not that I can't afford to spend more, but I don't have space for all my stuff as it is, so I want to limit acquisitions until I've assembled/painted/used (or sold) more of the mountain that I already have.
For the record, this includes things like glue and paint, and other non-hobby items bought for hobby use, but does not include membership or attendance fees for clubs and tournaments (not that I spend much on such things).